Access control security systems are employed to provide a restricted or controlled entry to a particular place or controlled security area. Such systems typically require detailed information concerning the identity of the user, the associated passcodes, and the schedules during which the user will be permitted access to the controlled area. If the total information is sufficiently large in number of pieces of data, such data will be stored in a centralized location, typically with a control console. However, for many facilities, such centralized control for access control systems is undesirable or unfeasible. Under such conditions, the access control systems must be self-contained and reside within the card reader or code entry housing.
When the access control systems are self-contained, it is necessary to enter the particular data concerning the user identification, passcodes, and schedules. Typically, such information should not be entered in a manner which would permit unauthorized personnel to have an opportunity to enter the system. Entry of user information by remote data links or programmable cards also presents problems when the information to be loaded is significant in length, or where the unit is remote from the centralized database. However, complicated entry methods further inhibit the ease and reliability of data entry, thereby reducing the effectiveness of the access control system in environments in which large volumes of information are to be entered, or in which information changes frequently.
Moreover, in self-contained access control systems, the processor operation must provide all system functions including timer update, information database management and card and keyboard reading functions. Typically, the card reader signal may be monitored in sequence with the other system function. However, the card reader signal, typically a sequence of pulses derived from the passage of a magnetic medium through an analog sensing curcuit, has wide variations in signalcharacteristic, which may place a burden on the processor for accurate detection of encoded card signals. If the card reader signals are polled at widely spaced intervals, the card reader operation may be unreliable, or require careful processing to reconstruct a valid signal.